Operating machinery may generate noise-causing vibrations. Modern aircraft may include various turbine systems such as jet engines (i.e., one or more gas-powered turbine engines), auxiliary power units (APUs), and/or environmental control systems (ECSs), which can generate both thrust to propel the aircraft and electrical and pneumatic energy to power systems installed in the aircraft by the flowing of a fluid, such as air, there-through. Although such aircraft systems are generally safe, reliable, and efficient, they can exhibit certain drawbacks. For example, turbine engine systems can be sources of noise, especially during aircraft take-off and landing operations. Additionally, APUs and ECSs can be sources of ramp noise while an aircraft is parked at the airport.
To mitigate the noise emanating from aircraft, various types of noise reduction systems have been developed. For example, noise suppression panels have been incorporated into some aircraft ducts and plenums, or into other channels and conduits that direct the flow of fluid relative to a solid object. Typically, noise suppression panels have flat or contoured outer surfaces, and include either a bulk absorber material or a honeycomb structure disposed between a backing plate and a face plate. The noise suppression panels are placed proximate the noise-generating source, such as on an interior surface of an engine or in an APU inlet and/or outlet ducts, as necessary, to reduce noise emanations.
Although the above-described noise suppression panels exhibit fairly good noise suppression characteristics, they may be improved. In particular, with the advent of additive manufacturing techniques, noise suppression panel configurations may become possible that were heretofore too costly or too complex to practically implement using conventional manufacturing technologies. Hence, there is continuing need for improved noise suppression configurations that take advantage of the latest manufacturing technologies to reduce manufacturing costs and increase noise suppression performance. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.